Auxiliary control means for pulse producing circuit



Jan. 6, 1959 w. L. GRYDER ET AL 2,867,200

AUXILIARY CONTROL MEANS FOR PULSE PRODUCING CIRCUIT Filed March 20, 1957 o+|2v DC R4 R2 RI Tl T FIG! #OUTPUT IO A:

OUTPUT ll J+|2v DC RECTIFIER DIFFERENTIATING L o |5 CIRC T 20 2| F|G.| J

MONOSTABLE MULTIVIBRATOR WILLIAM L. GRYDER L. --9 INVENTOR.

Y WW Q T ORNEYS DIFFERENTIATING/ B cmcun" GLENN 1.. HAUGEN United States Patent() AUXILIARY CONTROL MEANS FOR PULSE PRODUCING CIRCUIT William L. Gryder and Glenn L. Haugen, Baltimore, Md., assignors to Bendix Aviation Corporation, Towson, Md., a corporation of Delaware Application March 20, 1957, Serial No. 647,397

6 Claims. (Cl. 123179) This invention relates to means for producing a series of pulses of controllable duration and pulse repetition frequency and more particularly to an auxiliary means for controlling the duration of the pulses.

Such a pulse producing means, while generally useful, finds a particular use in systems of fuel injection for internal combustion engines in which fuel under pressure is fed to valves individual to the engine cylinders and the valves are solenoid actuated in synchronism with engine operation. The pulses are distributed by commutating devices to the various solenoids. 1

For engine speeds above a certain limit, it has been found necessary to utilize a pair of pulse producing means with the pulses of their outputs inter-mixed in alternation. A means is normally provided for controlling the duration of the pulses, the means being manually operable for the control of response to engine demands for power.

The starting of such engines, particularly in cold weather, creates fuel demands which are not met by the control means provided for normal operation and it is desirable to provide an auxiliary control for pulse duration to meet the needs peculiar to cold starting.

It is an object of this invention to provide an auxiliary control means for a dual channel pulse producing means for fuel injection in internal combustion engines which automatically responds to the action of starting the engine to increase the pulse duration and also varies the pulse duration as a function of engine temperature.

It is a further object of the invention to provide such a means which will introduce no interaction between the two pulse producing means of the dual system at engine cranking speeds.

It is another object of the invention to provide such a means which is simple and inexpensive.

These and other objects and advantages of the invention are realized by a means which actuates a pulsewidth controlling biasing means common to the two channels,

the bias control means being automatically actuatedthrough a fixed increment as long as the starter switch of the engine is closed and being further actuated in response to a temperature sensitive control means.

In the drawing:

Figs. 1 and 1a show a schematic diagram of a control circuit embodying the invention; and,

Fig. 2 is a schematic diagram of a modification of the circuit of Fig. 1.

In the drawing, the pulse producing means of' the two channels are indicated as a pair of transistorized monostable multivibrators M and M The multivibrator M comprises a pair of transistors T and T which' are indicated as being of the PNP junction type. Their emitters are connected through a common resistor R to a terminal 1, which is a positive terminal of a D. C. voltage source which is indicated as having a, value of. 12 volts. The terminal 1 is also connected through a resistor R to the base of transistor T This base electrode is also connected to ground by way of a resistor R The terr 2,867,200 Patented Jan. 6, 1959 minal 1 is also connected to ground through a serial string of resistors R and R A slider 4 in contact with resistor R is connected to the junction of resistor R and the corresponding resistor R5 of multivibrator M The collector of transistor T is connected by way of a resistor R to ground. The collector of T is connected to ground by way of a resistor R The base electrode of T is connected by way of a serial string of resistors R R and R to ground. A slider 5 coacts with resistor R and is connected to the junction of resistors R and R and also by way of a capacitor C to ground. The resistor R is also provided with a slider 6 connected to the junction of resistors R and R The slider 6 is actuated by way of a mechanical linkage indicated by the dashed line 7 in response to movement of a slug or armature 8 surrounded by an inductor 10. One end of the armature 8 is also secured to an end of a bimetallic temperature sensitive spring member 11 formed in the shape of a spiral, and having its other end fastened to a post or other fixed element 12. The coil 10 is part of a series circuit which includes a battery 13 and the starter switch 14 of the engine. The battery 13 may be the same voltage source energizing the terminal 1.

The collector of transistor T is coupled to the base electrode of transistor T by a capacitor C A terminal 15 is connected to the collector of T and an output terminal 16 is connected to the collector of T The multivibrator M is, in most respects, identical with M and its common components are indicated by the same reference characters as used with respect to multivibrator M the reference characters being primed. The resistor R, has its slider 5 connected to the junction of the resistors R and R The resistor R 0, its slider and the control means therefor, exercise their control function on both multivibrators.

A monostable multivibrator M shown in Fig. 1a, has its output applied to a difierentiating circuit 20 and thence by way of a rectifier 21 to the terminal 15. Another out put of multivibrator M oppositely phased from the first output, is applied to a differentiating circuit 20' and thence to terminal 15. The signals applied at the terminals 15, 15 are trains of positive going impulses as indicated by the graphs 18, 18'.

In Fig. 2 the resistor R has one of its terminals connected to ground and the other to a positive terminal 17 of the 12 volt source. The slider 6 is connected to the junction of R and R The slider 5 of R and the corresponding slider 5', of R are connected to the same junction.

In the operation of the circuit of Fig. l the multivibrators M and M operate in the same manner and, accordingly, only the operation of the multivibrator M will be explained. The values of the resistor R and R are such that the voltage at the base electrode of T is normally more positive than that existing at the emitter,

thereof. T is, therefore, normally in a non-conducting state. T is normally conducting to saturation with a voltage at the base electrode thereof more negative than that existing at its emitter. A series of positive-going voltage impulses, as indicated by the graph 18, is applied at the terminal 15. Each of these impulses is coupled to the base electrode of T by means of the capacitor C causing conduction to be lowered in that transistor. This, by virtue of the common resistor R causes the emitter of T to be raised in voltage to the point where conduction commences in transistor T The initiation of conduction will cause the collector of that transistor to become more positive, thus driving the base of T in a more positive direction and this regenerative action will cause T to be cut off and T to conduct a saturation. This condition will persist until condenser C discharges through resistors R R R and R to the point where the.

voltage on the base'electrode of T has fallen suthciently for conduction to be initiated in transistor T This will reduce the conduction in T and this regenerative action Will persist until the multivibrator has reverted to its stable state. The time elapsing betweenthe beginning of the astable state and the reversion to the stable state is governed primarily by the position "of the slider 4 on resistor R This controls the bias voltage applied across the resistor R to the collector electrode of T The slider 4 is normally driven, in the case of a fuel injection system, by a connection to the manifold of the engine and its position along the resistor R is thus a function of the manifold pressure.

The multivibrator M is driven in the same fashion by an identical series of voltage impulses 18' applied to the terminal The pulses of this series are, however, off.- set in time from those of the series applied to the multivibrator M so that the pulses of the two series occur in alternation. This is accomplished by commutating devices synchronized with engine operation and forming no 1 part of this invention. By way of example, however, there is shown in Fig. 1a, a block diagram of a circuit arrangement which could be used to provide the signals 18, 18'. A monostable multivibrator M which could be triggered by an engine driven commutator, has two These outputs applied to differentiating circuits 20, 20. outputs are square waves and are taken at such points in the multivibrator circuit that they are oppositely phased. The difierentiatior and rectification of these signals in the circuits 20, 21 and 20, 21 will produce positive going pulse trains of the form shown at 18 and 18' with the pulses of each train occurring in alternation with those of the other. Such an arrangement is shown in U. S. Patent 2,747,096, to Brockway et al., issued May 22, 1956, where the tubes 7 and 8' constitute a multivibrator such as M Outputs are taken from the plates of these tubes and applied respectively by lead 46, differentiating circuit 47, 50 to rectifier 48, and by leads 26 and 43 and differentiating circuit 44, 49 to rectifier 45. The rernaintier of the operation of multivibrator M is identical with that described with respect to M I The control means which governs pulse duration, as described above, operates satisfactorily for normal conditions of engine operation, except at the time of starting the engine and particularly when this occurs in cold weather. Under such conditions a pulsewidth greatly in excess of those required for normal running is necessary to provide Sllfl'lClCHt fuel to start the engine and maintain it in operation until it has warmed up. This additional pulse duration is provided by means of the resistor R and its associated mechanism. The resistor R forms with its slider 6 a potentiometer which, under normal warm running conditions, is completely short-circuited. The slider 6, driven by the linkage 7, is positioned in accordance with the position of the armature 8 of solenoid 10. The winding of this solenoid is in circuit with the starting of the switch 14 and the battery 13. 'The position of the armature 8, when the solenoid is deenergized, is governed by its connection to the temperature responsive spring 11. When the engine is warm, the spring, which is usually situated in close proximity to the manifold, will position the slider so that the resistor R is completely shortcircuited. When the engine is cold the slider will be so positioned as to include a small portion of the resistor R in the multivibrator circuit. When the starter switch 14 is closed and the solenoid 10 energized, the armature 8 will be withdrawn within the solenoid to the extent perrnitted by the spring 11, and a corresponding additional length of the resistor R will be included in the circuit.

When the starting action is completed and the switch 14 again opened, the position of the armature 8 will again be governed by the spiral spring 11.

K The, purpose of the potentiometers R and R is to j; p j l 2,867,200

. 4 equalize the operation of the two multivibrators with respect to pulse duration.

The potentiometer R operates, during starting and warm up, to greatly increase the resistance in the RC pulsewidth determining circuit including the capacitor C and the resistors R R a portion of R and R This operation will normally occur only when the potentiometer R isalready providing a large pulsewidth, say of four or five milliseconds duration. It also occurs only at the low cranking and idling speeds. As long as the resistance in the base leg of T remains an appreciable part of the total resistance of the RC circuit, there will be no appreciable interaction between the two multivibrators until a high repetition rate is reached.

Should more complete freedom from interaction be .and the remaining terminal grounded. The slider is connected to the junction of R and R with the capacitor C omitted.

This form of the invention varies the bias applied to the RC circuit rather than the resistance.

What is claimed is:

l. In a dual channel pulse producing system for producing a pair of pulse trains with the pulses of said trains occurring in alternation, said system comprising a pair of monostable multivibrators and means triggering said multivibrators in alternation, each of said multivibrators comprising a pair of amplifying stages, regenerative feedback means coupling said stages, capacitive means coupling the output of a first of said stages to the input of the second, a resistive discharge circuit for said capacitive coupling means, and means variably biasing said capacitive coupling means to provide a first control of the duration of the pulses of the output of said multivibrator: the combination therewith of means for additionally controlling said pulse duration operable to automatically increase said duration as a function .of a localized temperature variation within a selected range and to further increase said duration bya fixed amount in response to the completion of a control circuit, the last named means com prising a potentiometer connected to said discharge circuit in a manner to vary the discharge time thereof as the setting of said potentiometer is varied, an element reciprocable along a certain path, means connecting said element and said potentiometer whereby the setting of said potentiometer is varied by movement of said element along said path, temperature deformable means connecting said element to a fixed point and operable with change of temperature within a given range to variably position said element along a portion of said path, and a solenoid operable on said element when said control circuit is complete to move said element along the remainder of said path.

2. In a dual channel pulse producing system for producing a pair of pulse trains with the pulses of. said trains occurring in alternation, said system comprising a pair of monostable multivibrators and means triggering said multivibrators in alternation, each of said multivibrators comprising a pair of amplifying stages, regenerative feedback means coupling said stages, capacitive means coupling the output of a first of said stages to the input of the second, a resistive discharge circuit for said capacitive coupling means, and means variably biasing said capacitive coupling means to provide a first control of the duration of the pulses of the output of said multivibrator: the combination therewith of means for additionally controlling said pulse duration operable to automatically increase said duration as a function of a localized temperature variation within a selected range and to further increase said duration by a fixed amount in response to the completion of a control circuit, the last named means comprising a potentiometer forming a part of said discharge circuit and thereby varying the discharge time thereof as the setting of said potentiometer is varied, means connecting said element and said potentiometer whereby the setting of said potentiometer is varied by movement of said element along said path, an element reciprocable along a certain path, temperature deformable means connecting said element to a fixed point and operable with change of temperature within a given range to variably position said element along a portion of said path, and a solenoid operable on said element when said control circuit is complete to move said element along the remainder of said path.

3. In a dual channel pulse producing system for producing a pair of pulse trains with the pulses of said trains occurring in alternation, said system comprising a pair of monostable multivibrators and means triggering said multivibrators in alternation, each of said multivibrators comprising a pair of amplifying stages, regenerative feedback means coupling said stages, capacitive means coupling the output of a first of said stages to the input of the second, a resistive discharge circuit for said capacitive coupling means, and means variably biasing said capacitive coupling means to provide a first control of the duration of the pulses of the output of said multivibrator: the combination therewith of means for additionally controlling said pulse duration operable to automatically increase said duration as a function of a localized temperature variation within a selected range and to further increase said duration by a fixed amount in response to the completion of a control circuit, the last named means comprising a potentiometer having its slider connected to said discharge circuit and a source of voltage connected between its terminals thereby varying the discharge time of said discharge circuit as the setting of said potentiometer is varied, an element reciprocable along a certain path, means connecting said element and said potentiomi eter whereby the setting of said potentiometer is varied by movement of said element along said path, temperature deformable means connecting said element to a fixed point and operable with change of temperature within a given range to variably position said element along a portion of said path, and a solenoid operable on said element when said control circuit is complete to move said element along the remainder of said path.

4. In a dual channel pulse producing system for producing a pair of pulse trains with the pulses of said trains occurring in alternation, said system forming part of a fuel injection system for an internal combustion engine wherein said pulses individually actuate respective valves of said fuel injection system, said pulse producing system comprising a pair of monostable multivibrators and means triggering said multivibrators in alternation, each of said multivibrators comprising a pair of amplifying stages, regenerative feedback means coupling said stages, capacitive means coupling the output of a first of said stages to the input of the second, a resistive discharge circuit for said capacitive coupling means, and means variably biasing said capacitive coupling means to provide a first control of the duration of the pulses of the output of said multivibrator: the combination therewith of means for additionally controlling said pulse duration to automatically increase said duration as a function of the temperature existing at the manifold of said engine 'and to further increase said duration by a fixed amount in response to the completion of the starting circuit of said engine, the

' last named means comprising a potentiometer connected to said discharge circuit in a manner to vary the discharge time thereof as the setting of said potentiometer is varied, an element reciprocable along a certain path, means connecting said element and said potentiometer whereby the setting of said potentiometer is varied by movement of said element along said path, temperature deformable means connecting said element to a fixed point at said manifold and operable with change of temperature within a given range to variably position said element along a portion of said path, and a solenoid operable on said element when said starting circuit is completed to move said element along the remainder of said path.

5. In a dual channel pulse producing system for producing a pair of pulse trains with the pulses of said trains occurring in alternation, said system forming part of a fuel injection system for an internal combustion engine wherein said pulses individually actuate respective valves of said fuel injection system, said pulse producing system comprising a pair of monostable multivibrators and means triggering said multivibrators in alternation, each of said multivibrators comprising a pair of amplifying stages, regenerative feedback means coupling said stages, capacitive means coupling the output of a first of said stages to the input of the second, a resistive discharge circuit for said capacitive coupling means, and means variably biasing said capacitive coupling means to provide a first control of the duration of the pulses of the output of said multivibrator: the combination therewith of means for additionally controlling said pulse duration to automatically increase said duration as a function of the temperature existing at the manifold of said engine and to further increase said duration by a fixed amount in response to the completion of the starting circuit of said engine, the last named means comprising a potentiometer forming a part of said discharge circuit and thereby varying the discharge time thereof as the setting of said potentiometer is varied, an element reciprocable along a certain path, means connecting said element and said potentiometer whereby the setting of said potentiometer is varied by movement of said element along said path, temperature deformable means connecting said element to a fixed point at said manifold and operable with change of temperature within a given range to variably position said element along a portion of said path, and a solenoid operable on said element when said starting circuit is completed to move said element along the remainder of said path.

6. In a dual channel pulse producing system for producing a pair of pulse trains with the pulses of said trains occurring in alternation, said system forming part of a fuel injection system for an internal combustion engine wherein said pulses individually actuate respective valves of said fuel injection system, said pulse producing system comprising a pair of monostable multivibrators and means triggering said multivibrators in alternation, each of said multivibrators comprising a pair of amplifying stages, regenerative feedback means coupling said stages, capacitive means coupling the output of a first of said stages to the input of the second, a resistive discharge circuit for said capacitive coupling means, and means variably biasing said capacitive coupling means to provide a first control of the duration of the pulses of the output of said multivibrator: the combination therewith of means for additionally controlling said pulse duration to automatically increase said duration as a function of the temperature existing at the manifold of said engine and to further increase said duration by a fixed amount in response to the completion of the starting circuit of said engine, the last named means comprising a potentiometer having its slider connected to said discharge circuit and a source of voltage connected between its terminals, thereby varying the discharge time of said discharge circuit as the setting of said potentiometer is varied, an element reciprocable along a certain path, means connecting said element and the slider of said potentiometer whereby the setting of said potentiometer is varied by movement of said element along said path, temperature deformable means connecting said element to a fixed point at said manifold and operable with change of temperature within a given range to variably position said element along a portion of said path, and a solenoid operable on said element when said starting circuit is completed to move said element along e rem nder of said path.

No references cited. 

